Abstract This paper presents evidence for a regular sound change in 12th-century Old French where word-initial /k/ voiced to /ɡ/ before /la/ or /ra/. My treatment is the first to propose a unified account, as due to a regular sound change, for 13 reflexes of inherited etyma and 4 reflexes of Germanic borrowings that all exhibit velar onset voicing (VOV) contemporaneously. A dating in the late 12th century for VOV is supported by both corpus evidence and how it is bled, counterbled, and fed by other sound changes whose dating is established in prior literature. The ultimate origins of this Old French velar onset voicing most likely lie in an older and phonetically conditioned synchronic voicing process that originally operated both word-internally and at boundaries. Word-internally, where conditioning was static, the alternation became a phonemic difference and thereafter lost productivity relatively early. But synchronic alternation continued at boundaries, where its conditioning continued to depend on the adjacent word. It survived in a progressively reshaped manner word-initially, until the late 12th century, when this voicing alternation, now much narrower in scope, gave rise to VOV as a regular diachronic sound change. Previous treatment of the words in question considered each only in isolation, bypassing the chance to consider the proposed regular sound change as a possibility. Thus, this study shows the importance of considering both lexically focused approaches and the probing for regular sound changes as necessarily complementary methods.